A dense α-Si3N4/Sialon ceramic coating was fabricated on porous Si3N4 ceramic using the liquid infiltration and filling method. The effect of sintering temperature on microstructures, water absorption, mechanical properties and erosion resistance of the coatings were investigated in detail. The results showed that the coatings mainly consisted of α-Si3N4, O′-Sialon and Y–Si–Al–O–N glass, and the content of O′-Sialon increased gradually with the increase of sintering temperature. As-prepared coatings exhibited good waterproof ability though some pores were produced within the coating, and water absorption of porous Si3N4 ceramic decreased obviously after fabricating the coatings. Hardness, elastic modulus and E/H value of the coatings increased gradually as the sintering temperature increased from 1400 to 1450 °C, but they began to decrease when the sintering temperature reached 1500 °C. The coating prepared at 1450 °C displayed the best erosion resistance, and mass loss was only 0.91 wt% after eroding 2 h.
